Simparica Products for Fleas, Ticks, and Heartworms in Dogs

Medically Reviewed by Joshua Conrad, PharmD on October 20, 2024
Written by Kathleen Claussen, DVM
6 min read

The Simparica line of products (manufactured by Zoetis) includes chewable tablets (products that are given by mouth) for the prevention, control, and treatment of fleas, various tick species, and heartworms in dogs.  Simparica products are approved by the FDA for various antiparasitic uses in dogs depending on which product is being used.  These uses include treatment and prevention of flea infestations, treatment and control of various ticks, prevention of heartworm disease, and treatment of intestinal roundworms and hookworms.

All Simparica products for fleas and ticks contain the active ingredient sarolaner. Sarolaner is classified as an isoxazoline ectoparasiticide for treating and preventing fleas and ticks.  Simparica Trio also contains moxidectin and pyrantel.  Moxidectin is classified as a macrocyclic lactone antiparasitic that is used to prevent heartworm disease and to treat intestinal roundworms and hookworms.  Pyrantel is a cholinergic agonist anthelmintic for the removal of roundworms and hookworms.  

There are two Simparica chewable tablet options: Simparica or Simparica Trio.  Simparica chewable tablets are labeled for monthly protection (protection lasting 35 days) against fleas and ticks. Simparica Trio chewable tablets are labeled for one month (every 30 days) of protection against fleas, ticks, heartworm disease, roundworms, and hookworms.  

There are also some other uses for Simparica products in dogs, including being effective against certain types of mange and ear mite infestations.  These uses are “extra-label” or “off-label,” meaning that there is evidence of safe and effective use, even if FDA approval has not been received for the specific use or animal.

Simparica products are usually well tolerated in animals. There is minimal risk for overdose, side effects, or drug interactions if used as labeled or as directed by your veterinarian.

Simparica products are available from your veterinarian or with a prescription from your veterinary pharmacy.

Simparica and Simparica Trio are chewable tablets that you give to your dog by mouth once a month (every 30 days).  The chews can be given with or without food.  If your dog throws up or acts sick after being given a chew on an empty stomach, give the next chew with food or a small treat.  Simparica products should be eaten completely to be effective against their labeled parasites.  They need to be chewed or broken into smaller pieces before being eaten.  

Dogs and puppies should be at least 6 months old and weigh at least 2.8 pounds (1.3 kilograms) to use Simparica. Dogs and puppies should be at least 8 weeks old and weigh at least 2.8 pounds (1.3 kilograms) to use Simparica Trio.  

Always follow your veterinarian’s directions for giving medicines to animals.  Remember to tell your veterinarian about any medicines, vitamins, supplements, or herbal therapies that you are giving your pet. Talk to your veterinarian before stopping any pet medicines.  

  • Sarolaner (contained in all Simparica products) is licensed by the FDA for the treatment and control of fleas and various ticks in dogs.
  • Sarolaner with moxidectin and pyrantel (Simparica Trio ) is licensed by the FDA to protect against fleas, various ticks, heartworms, roundworms, and hookworms.
  • Simparica products can be used in dogs and puppies weighing as little as 2.8 pounds (1.3 kilograms).
  • With sarolaner, fleas start dying three hours after Simparica products are given and 100% of fleas are killed within 24 hours.
  • With sarolaner, there is a 99% effectiveness against ticks within the first 48 hours.

You and your veterinarian should monitor your pet for signs that the medicine is working (absence of live fleas or ticks) as well as for side effects of the medicine.  There is no routine lab monitoring needed with Simparica products.

If Simparica Trio is used for intestinal parasites, follow-up fecal (stool) tests may be checked.  If Simparica Trio is used for ear mites, follow-up ear tests may be done by your veterinarian.  If Simparica Trio is used for skin mite treatment, your veterinarian will monitor for improvement of symptoms (like hair loss and itching) as well as perform periodic skin tests.

Before giving Simparica Trio, dogs need to have a negative heartworm test.  The heartworm test should then be repeated yearly.  If there are missed doses of Simparica Trio, a heartworm test should be repeated before restarting the medication and then again in 6 months.  

Do not use a Simparica product in a dog that is allergic to its ingredients.  Do not use Simparica products in cats.  Use with caution in dogs that have a history of neurologic (nerve or brain) disease, including a history of seizures or epilepsy.  Do not use Simparica products in dogs below the minimum age or weight on the product label.  Use them with caution in older, weak, or frail dogs.  Use Simparica products with caution in breeding, lactating, or pregnant dogs.

Side effects are uncommon with Simparica products but may include:

  • Vomiting
  • Diarrhea (loose stool)
  • Decreased appetite
  • Lethargy (tiredness)

Sarolaner is a medicine in the isoxazoline drug class.  Isoxazoline drugs can cause neurologic (nerve and brain) side effects if given incorrectly or if an overdose occurs.  These issues include muscle tremors, ataxia (difficulty walking), and seizures.  Other serious side effects may include nonstop vomiting or complete loss of appetite.

If you think that your pet is having a serious side effect or may have been overdosed, call your veterinary clinic immediately. If it is outside of regular office hours, you may contact a local emergency veterinary hospital or an animal poison control center.

You can reach the ASPCA Animal Poison Control Center at 888-426-4435 or the Pet Poison Helpline at 855-764-7661.

Using multiple medicines can sometimes change how your pet’s medicines work or increase your pet’s risk for serious side effects.  Always tell your veterinarian about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements that your pet is using.

No significant drug interactions have been reported with sarolaner products when used at labeled doses.

Some medicines that may interact with the ingredient moxidectin in Simparica Trio are benzodiazepines such as alprazolam (Xanax) or diazepam (Valium), levamisole, and piperazine.  Other medicines to use cautiously with Simparica Trio are spironolactone, “azole” antifungals such as itraconazole or ketoconazole, cyclosporine, diltiazem, and erythromycin.  

This may not be a complete list of medicines that can interact with Simparica products. Always check with your veterinarian.

  • Keep Simparica products out of the reach of children.
  • Wash your hands with soap after handling Simparica products.
  • Do not handle Simparica products if you are allergic to any of the ingredients. 

Simparica products are very well tolerated by dogs and the risk of an overdose is low.  If you are concerned your pet is having an adverse reaction or if you suspect your pet has gotten more medicine than intended, call your veterinarian or veterinary emergency clinic immediately.

If your pet misses a dose, give the dose when you remember and then restart the dosing interval from that date. Do not double the dose of the medicine.  

If more than eight weeks have passed since the last dose of Simparica Trio, start the monthly chew again.  Your dog will need to have a heartworm test performed in six months to determine if there is heartworm disease. It takes six months from the bite of an infected mosquito until a dog may test positive for heartworm disease.

Store Simparica products in the original packaging at room temperature.  Protect them from light.